Synthesis of various nonbridged titanium(IV) cyclopentadienyl-aryloxy complexes of the type CpTi(OAr)X2 and their use in the catalysis of alkene polymerization. Important roles of substituents on both aryloxy and cyclopentadienyl groups

Article abstract of DOI:10.1021/om980106r

Various titanium complexes of the type Cp′Ti-(OAr)Cl₂ (Cp′ = cyclopentadienyl; OAr = aryloxy) could be prepared in high yields from Cp′TiCl₃. These complexes show remarkable catalytic activities for alkene polymerization with MAO or

Full text of DOI:10.1021/om980106r

2152
Organometallics 1998, 17, 2152-2154
Syn th esis of Va r iou s Non br id ged Tita n iu m (IV)
Cyclop en ta d ien yl-Ar yloxy Com p lexes of th e Typ e
Cp Ti(OAr )X2 a n d Th eir Use in th e Ca ta lysis of Alk en e
P olym er iza tion . Im p or ta n t Roles of Su bstitu en ts on
both Ar yloxy a n d Cyclop en ta d ien yl Gr ou p s
Kotohiro Nomura,* Naofumi Naga,† Misao Miki,‡ Kazunori Yanagi,‡ and
Akio Imai
Petrochemicals Research Laboratory, Sumitomo Chemical Company, Ltd.,
2-1 Kitasode, Sodegaura, Chiba 299-02, J apan
Received February 19, 1998
Summary: Various titanium complexes of the type Cp′Ti-
(OAr)Cl2 (Cp′ ) cyclopentadienyl; OAr ) aryloxy) could
be prepared in high yields from Cp′TiCl3. These com-
plexes show remarkable catalytic activities for alkene
polymerization with MAO or AliBu3-Ph3CB(C6F5)4: (C5-
Me5)Ti(O-2,6-iPr2C6H3)X2 (X ) Cl (2b), Me (8b), CF3-
SO3 (9b)) showed the highest activities. The bond angle
Ti-O-C (phenyl group) in 2b (173.0°) is significantly
different from those for other complexes (162.3-163.1°).
syntheses of various titanium complexes of the type
Cp′Ti(OAr)X2 (OAr ) aryloxy group) and their use in
the catalysis of alkene polymerization in the presence
of a cocatalyst. From these results, we also present an
important effect of substituents on the activity.
CpTi(OAr)Cl2 (1) or Cp*Ti(OAr)Cl2 (2) (Ar ) 2,4,6-
Me3C6H2 (a ), 2,6-iPr2C6H3 (b), 2-tBu-4,6-Me2C6H2 (c))
could be prepared in high yields from CpTiCl3 or
Cp*TiCl3 by adding 1 equiv of the corresponding lithium
phenoxides in diethyl ether (Scheme 1). Complexes
having other substituents on the cyclopentadienyl group
such as (nBuC5H4)Ti(O-2,6-iPr2C6H3)Cl2 (3b), (tBuC5H4)-
Ti(O-2,6-iPr2C6H3)Cl2 (4b ), (1,3-Me2C5H3)Ti(O-2,6-
iPr2C6H3)Cl2 (5b), and (1,3-tBu2C5H3)Ti(O-2,6-iPr2C6H3)-
Cl2 (6b), could also be prepared in the same manner
from the trichloride analogues, which were synthesized
by the reaction of TiCl4 with the corresponding Cp′SiMe3
in hexane (Scheme 2). These complexes could be
Alkene polymerization by homogeneous catalysis has
been one of the most attractive subjects in the field of
both organometallic chemistry and catalysis. There are
many reports concerning this topic using metallocene
analogues,1 hybrid “half-metallocene” complexes2 such
as (C5Me4SiR2NR)MX2, and others.3,4 On the other
hand, however, there is only one example for the
reaction catalyzed by nonbridged Cp′M(OR)X2 (Cp′ )
cyclopentadienyl group; X ) halogen, etc.) complexes
such as Cp*Ti(OiPr)Me2 (Cp* ) C5Me5),5 although the
syntheses of Cp-aryloxy complexes such as Cp*Ti(O-
2,6-Me2C6H3)Cl2 (2d ) were known.6 We thus believe
that it is still possible to develop this type of complex
as a polymerization catalyst not only because the
syntheses are relatively easy but also because the
catalyst can be compared with the hybrid half-metal-
locene analogues.2 In this paper, we wish to present
(3) Examples (recent report) for catalytic alkene polymerization
using group 4 metal complexes containing bis(amide) ligands: (a)
Canich, J . A. M.; Turner, H. W. WP 92/12162, 1992. (b) Horton, A. D.;
de With, J . J . Chem. Soc., Chem. Commun. 1996, 1375. (c) Cloke, F.
G. N.; Geldbach, T. J .; Hitchcock, P. B.; Love, J . B. J . Organomet. Chem.
1996, 506, 343. (d) Scollard, J . D.; McConville, D. H. J . Am. Chem.
Soc. 1996, 118, 10008. (e) Scollard, J . D.; McConville, D. H.; Payne,
N. C.; Vittal, J . J . Macromolecules 1996, 29, 5241. (f) Tinkler, S.; Deeth,
R. J .; Duncalf, D. J .; McCamley, A. J . Chem. Soc., Chem. Commun.
1996, 2623. (g) Nomura, K.; Naga, N.; Takaoki, K.; Imai, A. J . Mol.
Catal., in press. (h) Baumann, R.; Davis, W. M.; Schrock, R. R. J . Am.
Chem. Soc. 1997, 119, 3830. (i) Horton, A. D.; de With, J .; van der
Linden, A. J .; van der Weg, H. Organometallics 1996, 15, 2672. (j)
Clark, H. C. S.; Cloke, F. G. N.; Hitchcock, P. B.; Love, J . B.;
Mainwright, A. P. J . Organomet. Chem. 1995, 501, 333. (k) Bei, X.;
Swenson, D. C.; J ordan, R. F. Organometallics 1997, 16, 3282. (l)
Tsukahara, T.; Swenson, D. C.; J ordan, R. F. Organometallics 1997,
16, 3303. (m) Kim, I.; Nishihara, Y.; J ordan, R. F. Organometallics
1997, 16, 3314. (n) Shah, S. A. A.; Dorn, H.; Voigt, A.; Roesky, H. W.;
Parisini, E.; Schmidt, H-.G.; Noltemeyer, M. Organometallics 1996,
15, 3176.
* To whom correspondence should be addressed. Present address:
Research and Education Center for Material Science, Nara Institute
of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101,
J apan. E-mail: nomurak@ms.aist-nara.ac.jp.
† Present address: Research Laboratory of Resources Utilization,
Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama
226, J apan.
‡ Biotechnology Laboratory, Sumitomo Chemical Co., Ltd., 4-2-1
Takatsukasa, Takarazuka, Hyogo 665, J apan (X-ray crystallography).
(1) For example: (a) Brintzinger, K. H.; Fischer, D.; Mu¨lhaupt, R.;
Rieger, B.; Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34,
1143. (b) Guram, A. S.; J ordan, R. F. In Comprehensive Organometallic
Chemistry, 2nd ed.; Lappert, M. F., Ed.; Pergamon: Oxford, U.K., 1995;
Vol. 4, p 589.
(4) Examples of catalytic alkene polymerization using group
4
complexes that contain aryloxide ligands: (a) Miyatake, T.; Mizunuma,
K.; Seki, Y.; Kakugo, M. Macromol. Chem., Rapid Commun. 1989, 10,
349. (b) Canich, J . A. M. U.S. Patent 5,079,205, 1992. (c) van der
Linden, A.; Schaverien, C. J .; Meijboom, N.; Ganter, C.; Orpen, A. G.
J . Am. Chem. Soc. 1995, 117, 3008. (d) Fokken, S.; Spaniol, T. P.; Kang,
H.-C.; Massa, W.; Okuda, J . Organometallics 1996, 15, 5069. (e)
Sernetz, F. G.; Mu¨lhaupt, R.; Fokken, S.; Okuda, J . Macromolecules
1997, 30, 1562. (f) Fokken, S.; Spaniol, T. P.; Okuda, J . Organometallics
1997, 16, 4240.
(5) As far as we know, only one example was reported of ethylene
polymerization using the Cp*Ti(OiPr)Me2-[HNEt3]+[B(C6F5)4]- system
(4.08 kg of polymer/mol of Ti, ethylene 1 atm, benzene, room temper-
ature, 20 min): Stevens, J . C.; Neithamer, D. R. U.S. Patent 5,064,-
802, 1991.
(2) For example: (a) Canich, J . A. M. Eur. Patent 420,436. 1991.
(b) Canich, J . A. M.; Hlatky, G. G.; Turner, H. W. U.S. Patent 542,236
1990. (c) Stevens, J . C.; Timmers, F. J .; Wilson, D. R.; Schmidt, G. F.;
Nickias, P. N.; Rosen, R. K.; Knight, G. W.; Lai, S. Eur. Patent 416,-
815 A2, 1991. (d) Campbell, E. R., J r. U.S. Patent 5,066,741, 1991. (e)
LaPointe, R. E. Eur. Patent 468,651, 1991. (f) Okuda, J .; Schatten-
mann, F. J .; Wocaldo, S.; Massa, W. Organometallics 1995, 14, 789.
(g) Devore, D. D.; Timmers, F. J .; Hasha, D. L.; Rosen, R. K.; Marks,
T. J .; Deck, P. A.; Stern, C. L. Organometallics 1995, 14, 3132. (h) du
Plooy, K. E.; Moll, U.; Wocadlo, S.; Massa, W.; Okuda, J . Organome-
tallics 1995, 14, 3129. (i) Carpenetti, D. W.; Kloppenburg, L.; Kupec,
J . T.; Petersen, J . L. Organometallics 1996, 15, 1572. (j) McKnight, A.
L.; Masood, M. A.; Waymouth, R. M.; Straus, D. A. Organometallics
1997, 16, 2879.
(6) Gomez-Sal, P.; Martin, A.; Mena, M.; Royo, P.; Serrano, R. J .
Organomet. Chem. 1991, 419, 77.
S0276-7333(98)00106-X CCC: $15.00 © 1998 American Chemical Society
Publication on Web 05/08/1998

Communications
Organometallics, Vol. 17, No. 11, 1998 2153
Sch em e 1a
a
Ar ) 2,4,6-Me3C6H2 (a ), 2,6-iPr2C6H3 (b), 2-tBu-4,6-Me2C6H2 (c), 2,6-Me2C6H3 (d ).
Sch em e 2a
increased in 1-hexene polymerization (Table 1, runs
1-3),12 if the MAO which was prepared by removing
both toluene and excess AlMe3 was used as a cocatalyst.
The use of this MAO should also be a great advantage
in this catalysis to obtain polymers having unimodal
molecular weight distributions. It is also noteworthy
that 2b in the presence of MAO was also an effective
catalyst for copolymerization of ethylene with 1-butene
and of ethylene with 1-hexene (runs 12-14), and the
activities were higher than those for homopolymeriza-
tion of ethylene. The activity was almost the same as
that of by [Me2Si(C5Me4)(NtBu)]TiCl2 under the same
conditions. More detailed polymerization studies, in-
cluding the effect of cocatalysts, are in progress.
Legend: (i) nBuLi/hexane or KH/THF; (ii) Me3SiCl (excess);
a
(iii) TiCl4/hexane; (iv) LiO-2,6-iPr2C6H3/Et2O.
It turned out that other derivatives such as 1b,
2a ,c,d , and 3b-6b also show relatively high activity for
ethylene polymerization under the same conditions. The
activity catalyzed by Cp*Ti(OAr)Cl2 (2) with MAO falls
in the order OAr ) 2,6-iPr2C6H3 (2b; 1240 kg of PE/
((mol of Ti) h)) > O-2,6-Me2C6H3 (2d ; 1000) > O-2-tBu-
4,6-Me2C6H2 (2c; 446) > O-2,4,6-Me3C6H2 (2a ; 369) .
O-4-MeC6H4 (2e; 25),13,14 and (C5Me5)Ti(OiPr)Me2 showed
lower catalytic activity (44 kg of PE/((mol of Ti) h)) under
the same conditions. These results suggest that the
bulk of the aryloxide ligand containing substituents at
the 2,6-positions is important for high activity. On the
other hand, the effect of cyclopentadienyl substituents
on the activity with Cp′Ti(O-2,6-iPr2C6H3)Cl2-AliBu3/
identified by 1H and 13C NMR, mass spectroscopy,
elemental analysis, and X-ray crystallography.7
It turned out that 1b could also be prepared quanti-
tatively by the reaction of CpTiCl3 with an excess
amount of the phenol (in CH2Cl2 at room temperature),
whereas the reaction did not take place if Cp*TiCl3 was
used in place of CpTiCl3.7 Interestingly, reactions of
CpTiCl3 with an excess amount of 2,4,6-trimethylphenol
or 2,6-diisopropylphenol under reflux conditions in
toluene gave CpTi(O-2,4,6-Me3C6H2)2Cl (7a ) or CpTi-
(O-2,6-iPr2C6H3)2Cl (7b) in high yield (87 and 85%,
respectively),8 whereas the reaction of Cp*TiCl3 with
2,6-iPr2C6H3OH under the same conditions afforded 2b
in high yield (94%).
It is interesting to note that Cp*Ti(O-2,6-iPr2C6H3)-
Me2 (8b) could be prepared in high yield by the reaction
of Cp*TiMe3 with 2,6-iPr2C6H3OH in Et2O, although
attempts at isolation of 8b from 2b by the reaction with
MeMgBr, MeMgI, and MeLi were unsuccessful.9 It also
turned out that Cp*Ti(O-2,6-iPr2C6H3)(OTf)2 (9b; OTf
) CF3SO3) could be prepared from 2b with AgOTf in
high yield.10
-
Ph3C+B(C6F5)4 catalysts increased in the order Cp*
(2b; 2220 kg of PE/((mol of Ti) h)) . 1,3-tBu2C5H3 (6b;
653) > 1,3-Me2C5H3 (5b ; 215) > nBuC5H4 (3b ; 302),
tBuC5H4 (4b; 258) . C5H5 (1b; 77).15-17 It is evident
(11) It was also revealed that Cp*2TiCl2 and (2,6-iPr2C6H3O)2TiCl2
showed low catalytic activities for ethylene polymerization under the
same conditions (70 and 57 kg of PE/((mol of Ti) h), respectively). These
results suggest that the observed polymerization activity with 2b is
not due to Cp*2TiCl2 or (2,6-iPr2C6H3O)2TiCl2 which might be formed
by the disproportionation but is rather due to 2b. For detailed results,
see the Supporting Information.
It is important to note that 2b shows remarkable
catalytic activity for polymerization of ethylene, propy-
lene, and 1-hexene in the presence of MAO with
AliBu3/Ph3CB(C6F5)4 as a cocatalyst (Table 1). Com-
plexes 8b and 9b were also found to be effective, and
(12) Broad polydispersities were observed for the ethylene homo-
polymerization as compared to the narrow Mw/Mn values observed for
the polypropylene, poly-1-hexene, and ethylene/R-olefin copolymeriza-
tions. This is probably a result of polyethylene precipitation during
the polymerization, since these reactions were run at 60 °C.
(13) For experimental details, see the Supporting Information.
(14) The activity for ethylene polymerization with 2d -AliBu3-Ph3-
C+B(C6F5)4- catalyst under the same conditions of run 7 was 1570 kg
of polymer/((mol of Ti) h). The activity was lower than that with 2b-
2b and 9b with AliBu3/Ph3C+B(C6F5)4 showed the
-
highest activities for ethylene polymerization.11 It is
also important to note that the activity as well as the
molecular weight of the resultant polymer could be
AliBu3-Ph3C+B(C6F5)4 catalyst (2220 kg of polymer/((mol of Ti) h)).
-
(15) For experimental details, see the Supporting Information.
(16) A similar observation was reported for polymerization of styrene
with a series of Cp′Ti(OMe)3 complexes: Newman, T. H.; Campbell,
R. E.; Malanga, M. T. Metcon ’93, 1993; p 315. They mentioned that
these results suggested stabilization of the active site by electron-
releasing substituents.
(7) For detailed synthetic procedures of 1b, 2a -c,e, 3b, 4b, 5b, and
6b and analytical data, see the Supporting Information.
(8) For experimental details, see the Supporting Information.
(9) 8b: yield 77% (from Cp*TiMe3). For experimental details, see
the Supporting Information.
(10) 9b: yield 59%. For experimental details, see the Supporting
Information.
(17) (a) Randall, J . C. J . Polym., Sci., Polym. Phys. Ed. 1973, 11,
275. (b) J . Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29
(2&3), 201. (c) Annual Book of ASTM Standards; ASTM: Philadelphia,
PA, 1994; p D5017-91.

2154 Organometallics, Vol. 17, No. 11, 1998
Communications
Ta ble 1. Alk en e P olym er iza tion Ca ta lyzed by Cp *Ti(O-2,6-iP r 2C6H3)X2 (X ) Cl (2b), Me (8b), OTf (9b)) in
th e P r esen ce of Coca ta lyst
c
run no. cat. (amt/µmol)
cocat.
Al/Tia
olefin
temp/°C
time
polymer yield/g activityb 10-4 Mn Mw/Mn
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16
2b (10)
2b (2.0)
2b (2.0)
2b (4.6)
2b (4.2)
2b (6.5)
8b (8.5)
8b (3.1)
9b (3.7)
9b (3.9)
2b (13.2)
2b (2.3)
2b (2.3)
2b (2.1)
MAOd
1000 1-hexenee
r.t.
r.t.
r.t.
60
60
60
60
60
60
60
60
60
70
70
70
1 h
1.79
0.73
1.07
5.5
5.2
14.4
6.1
4.6
2.9
179
2190
1070
1200
1240
2220
718
1480
784
2100
568
17.4
26.0
29.9
2.77
13.8
9.17
15.1
1.87f
2.05
2.04
MAOg
1000 1-hexenee
10 min
30 min
1 h
1 h
1 h
1 h
1 h
1 h
1 h
1 h
1 h
1 h
1 h
MAOg
1000 1-hexenee
MAOd
1000 ethyleneh
14.8
MAOg
2000 ethyleneh
4.7
5.0
6.0
AliBu3/Bi
MAOg
500 ethyleneh
1000 ethyleneh
AliBu3/Bi
MAOg
500 ethyleneh
1000 ethyleneh
AliBu3/Bi
MAOd
500 ethyleneh
8.2
8.23
5.2
1.9
1.9
2.2
2.06
3.4
1000 propylenej
1000 ethylene/1-hexenei,k
1000 ethylene/1-butenem
1000 ethylene/1-buteneo
1000 ethylene/1-butenem
7.5
7.79
2.71
3.82
8.37
5.75
MAOg
4.7l
2040
7240
9290
6550
MAOg
16.8n
19.5n
17.8n
MAOg
CGC-Tip (2.7) MAOg
1 h
a
b
Molar ratio of Al/Ti. kg of polymer/((mol of Ti) h). c GPC data in THF (runs 1-3, and 14) or in o-dichlorobenzene (runs 4-13, 15, and
16) vs polystyrene standard. MAO 9.5 wt % (Al) in toluene. e 1-Hexene 15 g, cat. 5 µmol/g of toluene. f Small amount of low Mn peak was
d
also observed on GPC trace. g MAO (toluene solution) was evaporated in vacuo and was used as white solids. Ethylene 4 kgf/cm2, toluene
h
300 mL. B ) Ph3C+B(C6F5)4-, Ph3C+B(C6F5)4-/Ti ) 1 (molar ratio). Propylene 4 kgf/cm2. Ethylene 4 kgf/cm2, 1-hexene 10 mL. 1-
i
j
k
l
Hexene 15.4 mol % by 13C NMR,17 η 0.81 dL/g. Ethylene 6 kgf/cm2, 1-butene 10 g, toluene 200 mL. 1-Butene 21.0 (run 13), 32.0 (run
m
n
14), and 26.8 (run 15) mol %, respectively, by 13C NMR.17 o Ethylene 6 kgf/cm2, 1-butene 20 g, toluene 200 mL. [Me2Si(C5Me4)(NtBu)]TiCl2.
p
For experimental details, see the Supporting Information.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 1b, 2b, 2d , a n d 6ba
1b
2b
2d b
6b
Ti(1)-Cl(1)
Ti(1)-C(1)
Ti(1)-C(2)
Ti(1)-C(3)
Ti(1)-Cp
Ti(1)-O(1)
O(1)-C(6)
2.262(1)
2.282(8)
2.299(5)
2.325(5)
1.99
2.305(2)
2.367(7)
2.435(7)
2.368(7)
2.03
2.2736(6) 2.2553(8)
2.329(3)
2.341(2)
2.398(2)
2.034
2.379(3)
2.378(3)
2.410(2)
2.04
1.760(4)
1.772(3)
1.785(2)
1.366(3)
1.773(2)
1.365(3)
1.368(6)c 1.367(5)
Cl(1)-Ti(1)-Cl(2) 104.23(7) 103.45(5) 103.3(2)
103.46(3)
103.62(6)
98.57(6)
163.1(2)
119.3
Cl(1)-Ti(1)-O(1) 102.53(9) 99.1(2)
Cl(2)-Ti(1)-O(1) 102.53(9) 104.1(2)
101.7(1)
101.7(1)
162.3(2)
120.3
Ti(1)-O(1)-C(6)
Cp-Ti(1)-O(1)
Cp-Ti(1)-Cl(1)
Cp-Ti(1)-Cl(2)
163.0(4)c 173.0(3)
117.6
114.1
114.1
120.5
111.1
116.1
113.8
113.8
114.3
115.2
a
Legend: 1b, CpTi(O-2,6-iPr2C6H3)Cl2; 2b, Cp*Ti(O-2,6-iPr2C6-
H3)Cl2; 2d , Cp*Ti(O-2,6-Me2C6H3)Cl2; 6b, (1,3-tBu2C5H3)Ti(O-2,6-
iPr2C6H3)Cl2. See ref 6. c Ti(1)-O(1)-C(4).
b
OfTi π donation into the titanium. This along with
the more electron-donating Cp* (as compared to Cp,
t
BuCp, Me2Cp, and Bu2Cp) stabilize the active species
and leads to higher activity.16 We are thus studying
more concerning this catalysis: the results, including
both the reaction chemistry and the effect of cocatalysts,
will be introduced soon.
Ack n ow led gm en t. K.N. and N.N. express their
thanks to Mr. S. Kiuchi for experimental assistance.
K.N. also thanks Mr. A. Kondo for mass spectroscopy
and Y. Yagi for GPC analyses (Sumitomo Chemical Co.,
Ltd.).
F igu r e 1. Crystal structure of Cp*Ti(O-2,6-iPr2C6H3)Cl2
(2b): (top) Ortep drawing of 2b; (bottom) another view of
2b.
from these results that both Cp* and 2,6-diisopropyl-
phenoxy groups are indispensable for notable catalytic
activity.
Su p p or tin g In for m a tion Ava ila ble: Text giving experi-
mental details for the preparation of 1b, 2a -c,e, 3b, 4b, 5b,
6b, 7a ,b, 8b, and 9b with all analysis data and experimental
details for the polymerization of ethylene, propylene, and
1-hexene and copolymerization of ethylene with 1-butene and
of ethylene with 1-hexene and text, tables, and figures giving
experimental details for X-ray crystallography for 1b, 2b, and
6b (38 pages). Ordering information is given on any current
masthead page.
Table 2 summarizes selected bond distances and
angles for 1b, 2b,d and 6b determined by X-ray crystal-
lography. It is noteworthy that the bond angle Ti-O-C
(phenoxy group) for 2b (173.0°) is significantly different
from those of the others (162.3-163.1°), although no
significant differences were observed for both the bond
lengths and the angles among these compounds (Figure
1). It seems likely that the Cp* ligand sterically forces
the more open Ti-O-C angle, which leads to more
OM980106R